feat(json-abi): support legacy JSON ABIs #1711

Job	Run time
docs	35s
clippy	56s
fmt	11s
feature-checks	4m 46s
miri --no-default-features	1m 26s
wasm	1m 34s
miri	3m 46s
test stable --no-default-features	47s
miri --all-features	5m 39s
test stable	1m 3s
test stable --all-features	1m 45s
test beta --no-default-features	23s
test beta	56s
test beta --all-features	2m 1s
test nightly --no-default-features	36s
test nightly	59s
test nightly --all-features	1m 39s
test 1.65 --no-default-features	1m 40s
test 1.65	1m 41s
test 1.65 --features json	1m 34s
	33m 57s

Provide feedback